In order to meet these different expectations, the amphibious vehicle should be conformed so as to be used satisfactorily and as far as possible equivalently both on water and on firm ground. Further, it should be able to cross without any external help the intermediate region between the water and the ground and should notably be able to be adapted to the morphology of banks or shores. Finally, but without being exhaustive in the required characteristics of an amphibious vehicle which are met by the vehicle of the invention, the amphibious vehicle should be able to be used just as well alone as in a combination with one or more other vehicles of the same design, in order to form a pontoon.
In order to be able to meet both requirements of a road displacement and of being placed as a pontoon, the elements required for forming a bridge, such as caissons, floats, and ramps, have already been positioned in different ways on a vehicle forming a self-propelled rolling base. Among the different tested configurations, it is also found that of a rotating arrangement according to which the whole of the caissons, ramps and optionally floats form a pivotally mounted block on the rolling base. According to this design, when the vehicle is launched into the water, the longitudinal axis of the rolling base is approximately oriented parallel to the shore of the river or lake to be crossed. And when the vehicle is in position, the whole of the elements forming the bridge is rotated in one direction or in the other one by about 90° around a vertical axis.
However, the diversity of the morphologies of water-filled or dry openings to be crossed requires the possibility of adapting the arrangement of the elements forming a pontoon. In this sense, it proved to be disadvantageous to have to rotate the whole of the elements and/or having to deploy the whole of the elements.
Retractable or folding means for breaching dry or water-filled openings have been already used for a long time, mainly but not exclusively by military engineering. Such means have also already been used for some time on road vehicles or amphibious vehicles in order to give a certain autonomy to these breaching means, which is particularly important in a military application.
Thus, for example document FR-2 049 125 describes a bridge-shaped amphibious vehicle provided with floats placed above the chassis of the vehicle for moving over firm ground, these floats may be pushed back towards the outside on both sides for moving on water. In the folded-back configuration, the floats, which have a rectangular section, are placed with their narrow sides, side by side above the chassis of the vehicle, and are guided by connecting rods so that the wide sides turned towards each other, form a continuous covering surface after deployment of the floats. This vehicle has the disadvantage of a rather significant height in the folded-back configuration. Independently of the fact that such an outline involves a risk of instability when the vehicle is moving over irregular ground, it is easily understood that such a vehicle is more easily located than a flat vehicle.
A flatter vehicle is described in document FR-A-2 383 035. This is an amphibious vehicle intended to act as a pontoon or barge and including at least two floats which are put away over each other on the body of the vehicle while the latter moves over firm ground. This vehicle does not include any access ramps.
EP-A-1 332 896 describes an amphibious bridge and crossing vehicle comprising, in addition to a self-propelled main float and two tilting side floats, two sideways tilting foldable ramps, hydraulically moving up and down and each formed by a base of ramps and an end of ramps. In this amphibious vehicle, the kinematics of deployment of both side floats and of both ramps is rather complex, with the result that when the ramp base is unfolded and the ramp end is folded, the end of the ramp is found on the upper face of the ramp base and on the corresponding side float. Owing to this configuration of the amphibious vehicle, the floats and the ramps have to be entirely deployed in order to be able to use the vehicle.